1. Field of the Invention
The present invention relates to a hard disk drive, and more particularly, to a hard disk drive with a disk clamping apparatus to secure a data storage disk to a spindle motor.
2. Description of the Related Art
A hard disk drive reads data from and/or writes data to a disk by using a read/write head. During the reading and writing operations, the head is shifted to a desired position on the surface of the disk by an actuator, while flying over the recording surface of the spinning disk at a proper height.
FIG. 1 is an exploded perspective view illustrating one example of a conventional hard disk drive.
Referring to FIG. 1, the hard disk drive includes a base member 11, a spindle motor 30 mounted to the base member 11 for rotating a disk 20, which is a storage medium for storing data, and an actuator 40 for moving a read/write head to a desired position on the disk 20.
The spindle motor 30 is installed to the base member 11. The spindle motor 30 may be provided with two disks, as illustrated in FIG. 1, or may be provided with one or more disks. In the case where a plurality of disks are mounted to the spindle motor 30, a ring-shaped spacer 50 is positioned between each disk 20 to maintain a distance between the disks 20. A clamp 60 is engaged to an upper end of the spindle motor 30 by use of screws 70 to rigidly secure the disk 20 to the spindle motor 30.
The actuator 40 includes a swing arm 42, rotatably coupled to a pivot bearing 41 installed on the base member 11, a suspension 43 installed on one end portion of the swing arm 42 for supporting and elastically biasing a slider (not shown), on which the head is mounted, toward the surface of the disk 20, and a voice coil motor (VCM) 45 for rotating the swing arm 42. The voice coil motor 45 is controlled by a servo control system. The swing arm 42 is rotated in a direction according to the Fleming's left-hand rule by the interaction between an electric current input to a VCM coil and a magnetic field generated by magnets. Specifically, when the disk 20 starts spinning, upon the hard disk drive being turned on, the voice coil motor 45 rotates the swing arm 42 in a counterclockwise direction to move the head to a desired position on a recording surface of the disk 20. On the contrary, when the disk 20 stops spinning, upon the hard disk drive being turned off, the voice coil motor 45 rotates the swing arm 42 in a clockwise direction to move the head away from the disk 20. At this time, the head deviating from the recording surface of the disk 20 is parked on a ramp 46 provided outside of the disk 20.
A cover member 12 is assembled to the upper portion of the base member 11, using a plurality of screws 19. The disk 20, the spindle motor 30 and the actuator 40 are enclosed and protected by the base member 11 and the cover member 12 coupled to each other.
A conventional coupling structure of the spindle motor 30, the disk 20 and the clamp 60 will now be described with reference to FIGS. 2 and 3.
FIG. 2 is an enlarged perspective view illustrating a clamping portion of a conventional hard disk drive in FIG. 1, and FIG. 3 is a cross-sectional view illustrating a state where a conventional clamp shown in FIG. 2 is coupled to a spindle motor.
Referring to FIGS. 2 and 3, a shaft 32 is generally fixed to the spindle motor 30, and a hub 34 is rotatably installed to the shaft 32 of the spindle motor 30. The disk 20 is mounted around an outer periphery of the hub 34. In the case where a plurality of disks are mounted to the spindle motor 30, a ring-shaped spacer 50 is installed around the outer periphery of the hub 34 to maintain a distance between the disks. The clamp 60 is generally engaged to an upper end of the hub 34, using four or six screws 70. The clamp 60 is provided at a center portion thereof, with a hollow portion 62, and a plurality of screw-receiving holes 64 around the hollow portion 62 at constant intervals from the hollow portion 62. The clamp 60 is also provided along an outer edge thereof, with a pressing portion 68 for pressing the upper surface of the disk 20 in a vertical direction.
In this conventional hard disk drive, the operation of writing the data on the disk and reading the data from the disk is achieved by a read/write head on a rapidly spinning disk 20, with the read/write head flying on the disk at very small intervals. The inherently poor smoothness of the disk 20, or the poor smoothness of the disk 20 acquired during the fastening the clamp 60, is a major reason for generating error signals when the head writes data on the disk 20 or reads data from the disk 20. In particular, the smoothness defect of the disk 20, acquired from the fastening the clamp 60, is a result of a non-uniform distribution of stress applied to the disk 20 through the plurality of screws 70.
Specifically, when the clamp 60 is fastened to the spindle motor 30, using the plurality of screws 70, a pressing force acts on the disk 20 by the pressing portion 68 of the clamp 60. Even though the plurality of screws 70 are tightened with a precise torque, the torque applied to the respective screws 70 cannot be completely equal. Therefore, the pressing force applied to the disk 20 is not radially uniform, and hence, the disk 20 can become bent, as illustrated in FIG. 4, thereby deteriorating the smoothness of the disk 20.
Meanwhile, if the pressing force applied to the disk 20 is week, by tightening the screws 70 with insufficient torque, the disk 20 may slip when an external shock is applied to the hard disk drive. A slipping of the disk 20 causes the data to be recorded in a position away from a center line of a track. Accordingly, the head cannot search its original stored position or cannot serve to normally write and read the data.
In addition, since the clamp 60 is secured to the hub 34 of the spindle motor 30 by way of a plurality of screws 70, a lot of time is required to fasten the multiple screws 70. Also, the multiple screws 70 are fastened to the hub 34 of the spindle motor 30 by use of an electric driver. During this fastening, fine metal particles are generated due to friction between metals of the screws and the hub 34. These metal particles can cause a scratch to form on the surface of the disks 20 or the head to be damaged, thereby reducing the effectiveness of the writing/reading to/from the disk 20.
Various studies have been developed to solve the above problems. One example is disclosed in Japanese Patent Laid-Open Publication No. 2003-6970, where a disk is secured to a spindle motor by way of a clamp, without using a screw. An inner periphery of the clamp contacts a hub of the spindle motor with a sufficient resilient force to maintain a clamping state of the disk. However, the clamp does not mechanically prevent the disks from being separated. Accordingly, an inner periphery of the clamp can be lifted from its original position due to an external shock or vibration. In this case, a pressing force applied to the disks may be attenuated. Thus, in this method, there are disadvantages in that the clamp may secede from the hub, when the repeated external shock or vibration is repeatedly applied to the hard disk drive. In addition, it is difficult to manufacture the clamp since the clamp can be complicated.